Could Groundwater be the Key to Better Simulations of Heat Waves? Explicit Groundwater Representation in a State-of-the-art Regional Climate Model Ensemble over Europe

In future, heat wave strength, frequency and duration are expected to increase due to global change. Previous studies showed that current Regional Climate Models (RCMs) applied over the European continent exhibit a warm bias and tend to overestimate the frequency of heat waves. This study analyzed heat waves over a decadal evaluation period, comparing the Terrestrial Systems Modeling Platform (TSMP) to a representative EURO-CORDEX RCM ensemble, and a reference data set (E-OBS) based on observations. TSMP closes the terrestrial water cycle including 3D variably saturated groundwater flow. In the evaluation, TSMP provided consistently improved statistics with respect to observations in comparison to the RCM ensemble, which is attributed to the improved hydrology in TSMP including groundwater. In future RCM downscaling experiments, special attention should be paid to hydrological process representation.